The ACKR2-CCR2 axis in development and disease.

The movement of white blood cells (leukocytes) into and within tissues is regulated by specialised proteins called chemokines. Chemokines are produced by a range of cells and tissues and interact with molecules called receptors on the leukocytes. Therefore, for example, when a tissue becomes inflamed or infected it produces chemokines which then attract leukocytes to the inflamed sites. These leukocytes then kill invading bacteria and viruses and help to repair the damaged tissue. Chemokines are therefore extremely important biological regulators. The downside of chemokines, and their receptors, is that they are also involved in attracting leukocytes to previously healthy tissue sites to give rise to, what are called, autoimmune and inflammatory diseases. So, for example, in rheumatoid arthritis leukocytes are attracted inappropriately to joints and once there, instead of killing bacteria, they start to kill the tissue and cause profound problems for the patients. Chemokines and their receptors are therefore important targets for therapy.

We have a particular interest in molecules called 'atypical chemokine receptors'. These molecules fine-tune chemokine-driven responses and are involved in the regulation of leukocyte positioning within tissues. This proposed Programme of work relates specifically to one of these atypical chemokine receptors which is called ACKR2. ACKR2 destroys the chemokines which are involved in inflammation and it is therefore a 'negative regulator' of inflammatory responses. We have implicated it in a wide range of human inflammatory pathologies and have shown that it is essential for the resolution of the inflammatory response. In the current Programme Grant we propose to use basic scientific, and clinically focused, approaches to try to analyse the functions of ACKR2 in more detail. This is of importance as it will enhance our understanding of the overall orchestration of chemokine function and will provide novel potential therapeutic targets.

Specifically, in this Programme, we propose to examine novel roles for ACKR2 in the regulation of what is called the lymphatic system. This system is essential for the drainage of fluid from our tissues and is also an indispensable contributor to the development of immune responses. Data that we have generated so far indicate that ACKR2 is involved in establishing networks of lymphatic vessels and we propose to examine this in considerable detail. We will define the biological mechanisms behind this as well as the functional and pathological implications. Secondly the Programme will focus on new observations that we have made concerning the involvement of ACKR2 in the process of metastasis. Metastasis is frequently the terminal stage of cancer and it is metastasis that kills the vast majority of cancer patients. Mice that lack ACKR2 basically do not develop metastasis and we now propose to try to examine the mechanisms behind this. We also suggest that these data highlight ACKR2 as a potential therapeutic target for use in treating human metastasis. We will therefore generate compounds capable of inhibiting ACKR2 function and will test these in various models of metastasis.

Our in vivo approaches depend on a number of mouse strains all but one of which we currently have. We propose to generate a novel mouse strain in which ACKR2 expression is driven by tetracycline in a cell-specific manner. These mice will be important for a number of aspects of the proposed study and will be produced by Taconic who have extensive expertise in this area.

Finally, our plans to identify therapeutically relevant antagonists of ACKR2 function will benefit from access to a number of chemical libraries. We have an agreement with MRC-T for access to their compound library. In addition, through an agreement between the University of Glasgow and AstraZeneca (AZ), we have access to AZ chemical libraries and, importantly, to a library sub-selected for molecules able to interact with chemokine receptors. The existing agreement between the University and AZ allows us to screen these libraries with no commitment, other than first right of refusal, to AZ.

The wider academic community.
Through the proposed studies we will be importing, into the United Kingdom, a wide range of cutting-edge technologies that are not currently available in this country. Once established in Glasgow we will offer training to colleagues throughout the United Kingdom and also to International colleagues wishing to take advantage of our expertise. We will also generate a number of novel reagents and animal strains that will be of general used to the biological science community.

The commercial/private sector.
Therapeutic targeting of signalling chemokine receptors has been a major goal for the past two decades and yet only 2 molecules (Plerixafor and Maraviroc) have so far been licensed for clinical use and neither of these are currently being used in the context of immune and inflammatory diseases. This represents a major failure on behalf of the chemokine community. Our alternative plan, to try to therapeutically target the atypical chemokine receptors, therefore represents a novel approach to therapeutic interference in chemokine function. We propose that in the right circumstances, such as metastasis, small molecule antagonists of atypical receptors such as ACKR2 may well find therapeutic utility. One of the great advantages of targeting ACKR2 is that it will allow simultaneous interference with chemokines capable of interacting with any, or all, of CCRs1, 2, 3, 4 and 5 and thus will provide a nodal point for interfering with inflammatory CC-chemokine function. Proof of principle of the success of such an approach is provided by the study of viruses which have evolved a number of molecules capable of interfering with functions mediated by exactly these receptors. We therefore propose that a demonstration of the clinical utility of targeting atypical chemokine receptors will represent a very significant contribution to pharmaceutical industry approaches to the treatment of inflammatory, and related, disorders.

The wider public.
i) It is our hope that the novel therapetuic approach of tagetting the 'atypical' chemokine receptors will ultimately be of benefit to patients at least in the context of cancer metastasis.
ii) The MRC programme grant grouping provides outreach activity to schools and also supports school pupils who wish to carry out their Advanced Higher (Scottish A Level equivalent) Biology research projects. We have done this for the past 5 years with great success and have therefore built up excellent relationships with a number of local schools. This will be continued throughout the next quinquennial funding period.